STMicroelectronics SR1PBBU

Overview

SR1PBBU from STMicroelectronics is a 4-pin Smart Reset™ supervisory IC designed for reliable, push-button-initiated system reset control in ultra-low-power wearable electronics. It features factory-programmed 7.5 s Smart Reset setup delay (tSRC), 360 ms fixed reset pulse duration (tREC), active-low open-drain RST output with optional internal pull-up, and operates across 2 V–5.5 V supply at -40 °C to +85 °C.

For engineers reviewing the SR1PBBU datasheet, SR1PBBU pinout, SR1PBBU application, or SR1PBBU equivalent, this device delivers deterministic reset timing, test-mode diagnostics, glitch-immune input logic, and voltage-domain flexibility-critical for activity tracker power management, smartwatch recovery sequences, and compact sensor node reliability.

Technical Context

The SR1PBBU implements a dual-phase reset architecture: first, an extended tSRC delay (7.5 s typ.) ensures only intentional long-presses trigger reset; second, a factory-fixed tREC (360 ms typ.) guarantees consistent reset pulse width independent of button release timing. Its SR input includes internal pull-up (65 kΩ) and fixed logic thresholds (VIL ≤ 0.3 V, VIH ≥ 0.85 VCC), enabling robust operation across mixed-voltage domains.

Test mode activation requires overvoltage on SR (VCC + 0.9 V to VCC + 1.4 V), initiating a shortened tSRC-INI (42 ms typ.) and tSRC-SHORT (tSRC/128). The UDFN6 package supports high-density layout, while undervoltage behavior guarantees RST remains High-Z below 2.0 V, preventing spurious resets during brown-out conditions.

Key Specifications

Pinout & Package

SR1PBBU is housed in a 6-pin UDFN package (1.00 mm × 1.45 mm × 0.50 mm, 0.50 mm pitch), RoHS-compliant and halogen-free per ECOPACK®2. Pins 5 and 6 are not bonded and must be connected to VSS for mechanical stability and thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Smart Reset™ supervisory applications.

Compared with MAX6326TUT+T and TPS3808G12DBVR, SR1PBBU uniquely combines programmable long-delay initiation, fixed-duration reset assertion, integrated input pull-up, and voltage-domain-flexible open-drain output-making it the sole fit for wearable user-recovery systems requiring both safety and usability.

Availability

SR1PBBU is available at Aetrix Electronics and suitable for activity tracker recovery, smartwatch power-on sequencing, and smartglasses system reset applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SR1PBBU includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering innovative silicon solutions for automotive, industrial, and consumer markets since 1987.

SR1PBBU belongs to ST's Smart Reset™ supervisory IC product line, engineered specifically to replace mechanical reset buttons in space-constrained, battery-powered wearables-enabling intuitive, reliable, and maintenance-free user recovery.

FAQ

What is the function of the NC pins on SR1PBBU?

Pins 5 and 6 are not internally bonded and serve no electrical function. Per ST's datasheet (Section 3.1), they must be externally connected to VSS to ensure mechanical stability, optimal thermal dissipation, and compliance with UDFN6 assembly guidelines. Leaving them floating may cause solder joint reliability issues or thermal stress under repeated temperature cycling.

Can SR1PBBU operate with SR and VCC in different voltage domains?

Yes-SR1PBBU supports mixed-voltage operation. Its fixed SR input thresholds (VIL ≤ 0.3 V, VIH ≥ 0.85 VCC) and open-drain RST output allow SR to be driven from a separate domain (e.g., VBAT) while VCC powers the IC. To prevent inadvertent test mode entry, VCC must power up before or simultaneously with the SR domain to avoid V(SR) > VCC + 0.9 V.

How does the test mode work, and how is it exited?

Test mode activates when SR is driven to VCC + 0.9 V to VCC + 1.4 V, triggering a shortened tSRC-INI (42 ms typ.). Subsequent SR pulses use tSRC-SHORT (tSRC/128). Exit requires a full power cycle: VCC must drop to 0 V and re-ramp to its operating voltage. This ensures deterministic exit without relying on timing or external signals.

Is an external decoupling capacitor required for SR1PBBU?

Yes-a 0.1 µF ceramic capacitor is mandatory between VCC and VSS, placed as close as possible to the device. ST specifies this in Section 3.1 to suppress high-frequency noise and stabilize internal reference circuits during tSRC timing and reset assertion. Omission risks erratic reset behavior or failure to meet tREC timing specifications.